1. Field of the Invention
The present invention relates to antennas and in particular, to radio frequency antennas for transmitting and receiving radio frequency (RF) signals. Even more particularly, the present invention relates to a compact antenna, which is provided for use in connection with a radio frequency controlled lighting control system.
2. Description of the Related Art
Systems for controlling an electrical device by remote control are known. For example, prior art systems and methods control the status of electrical devices such as electric lamps, from a remote location via communication links, including radio frequency links, power line carrier links or infrared links. Status information regarding the electrical devices (e.g., on, off and intensity level) is typically transmitted between specially adapted lighting control devices and at least one master control unit. At least one repeater device may also be provided to help ensure reliable communications between the master control unit and the control devices for the respective electrical devices. The repeater may be required when a control device is unable to receive control signals transmitted directly from the master control unit, and, typically, employs a repeater sequence for helping to ensure that each receiver receives those signals intended for it.
Referring now to the drawing figures, in which like reference numerals refer to like elements, there is shown in FIG. 1A a prior art arrangement of a system 100 for remote control of electrical devices. The example prior art system 100 illustrated in FIG. 1A includes configurable devices that are manufactured by the assignee of the present patent application and commercially known as the RadioRA® lighting control system. The RadioRA® lighting control system is described in greater detail in commonly-assigned U.S. Pat. No. 5,905,442, issued May 18, 1999, entitled METHOD AND APPARATUS FOR CONTROLLING AND DETERMINING THE STATUS OF ELECTRICAL DEVICES FROM REMOTE LOCATIONS, the entire disclosure of which is hereby incorporated by reference.
As shown in FIG. 1A, the hardware devices include a master control unit 102, two control devices 104, a repeater 106, a car visor control 108 that may be mounted on an automobile's sun visor, and two electrical devices 110, e.g., lamps. The devices 102, 104, 106 and 108 transmit radio frequency signals 112, which can include control information and instructions regarding the respective electrical devices 110.
In the prior art system 100 illustrated in FIG. 1A, the control devices 104 are coupled to electrical devices 110 by wire connections, such as, for example, building wiring for providing power to electrical devices. Each control device 104 includes a communications and control circuit 114 that comprises a radio frequency transmitter/receiver 116 and an antenna 118 for transmitting/receiving the radio frequency signals 112. The antenna 118 is described in greater detail in U.S. Pat. No. 5,736,965, issued Apr. 7, 1998, and U.S. Pat. No. 5,982,103, issued Nov. 9, 1999, both entitled COMPACT RADIO FREQUENCY TRANSMITTING AND RECEIVING ANTENNA AND CONTROL DEVICE EMPLOYING SAME. The entire disclosures of both patents are hereby incorporated by reference.
The communications and control circuit 114 further includes a controller 120 for adjusting the status of the attached electrical device 110. The transmitter/receiver 116 receives the radio frequency signals via the antenna 118 and transmits a status radio frequency signal with information regarding the status of the controller 120 (which indirectly reflects the status of the connected electrical device 110). The controller 120 adjusts the status of the electrical device in response to the control information. Each control device 104 further includes button(s) 122 and dimmer control(s) 124, which are further operable to allow manual adjustment of the connected electrical device 110.
The master control unit 102 includes at least one actuator 126, at least one status indicator 128, a transmitter/receiver 116, and an antenna 118. The actuators 126 enable a user to control the electrical devices 110 remotely. The status indicators 128 indicate the status of the electrical devices 110. The transmitter/receiver 116 and the antenna 118 are operable for transmitting a radio frequency signal 112 having the control information therein to control the status of the electrical devices 110, as well as for receiving status information from the control devices 104.
The master control unit 102 can take several forms. For example, the master control unit 102 can be formed as a tabletop master, which plugs into an electrical outlet and includes a conventional antenna for transmitting and receiving signals. In another form, the master control unit 102 mounts on a wall, and is sized such that the master control unit 102 fits within the confines of a standard electrical wall box. In either form, the master control unit 102 includes a plurality of controls, each associated with a particular control device or a plurality of control devices. In the prior art, the user must program the association of the electrical control devices to a particular actuator 126 on the master control unit. Further, prior art master control units 102 must be programmed in order to provide functions allowing all control devices 104 to turn on or off substantially simultaneously.
The repeater 106 may receive radio frequency signals 112 (including status information and instructions) from the master control unit 102 and, thereafter, transmit radio frequency signals 112 to the control devices 104. Further, the repeater 106 may receive radio frequency signals 112 from the control devices 104 and, thereafter, transmit them to the master control unit 102.
The car visor control 108 provides a convenient and remotely usable interface to transmit radio frequency signals 112 to the master control unit 102, and may be disposed in a vehicle, for example, on a vehicle's interior sun visor. The buttons 130 are provided for remotely activating the master control unit 102. For example, the car visor control 108 can be used to cause a lighting scene to turn on/off, or may be operated to turn the electrical devices 110 on/off, via the master control unit 102.
Thus, the master control unit 102 is operable to generate radio frequency signals, which are transmitted to and received by the control devices 104, such as light dimmers, and/or the repeater 106. The control devices 104 use the information received in the radio frequency signals 112 to control the connected electrical devices 110 to a desired intensity. The control devices 104 preferably transmit radio frequency signals 112 via antennas 118 to the master control unit 102 (or to the master control unit 102 via the repeater 106) in order to indicate the status of the control devices 104 (and thus, the connected electrical devices 110). Using the respective devices, a combination of lighting controls in different or the same rooms of a structure, for example, can be instructed to turn on/off, thereby creating a lighting “scene” according to a user's desire.
FIG. 1B shows a front view of a prior art lighting control device 104 of the lighting control system 100 of FIG. 1A. Lighting control devices 104 preferably fit into standard electrical wall boxes. The antenna 118, which comprises a part of each control device 104, is sized so as to fit within the standard electrical wall box and is preferably disposed directly behind an actuator button 150 that is provided in the opening of a designer-style faceplate 160 as shown in FIG. 1B. An example of such an antenna is described in greater detail in co-pending commonly-assigned U.S. patent application Ser. No. 10/873,033 filed Jun. 21, 2004, now U.S. Pat. No. 7,362,285, entitled COMPACT RADIO FREQUENCY TRANSMITTING AND RECEIVING ANTENNA AND CONTROL DEVICE EMPLOYING SAME, the entire disclosure of which is hereby incorporated by reference.
However, it is desirable to provide an RF load control device that has an actuator button that is provided in the opening of a traditional-style faceplate. It is also desirable to provide an RF load control device that will work with a metal faceplate. Therefore, there is a need for an antenna that is disposed behind the actuator button that is provided in the opening of a traditional-style faceplate.